An answer is sought here to the question of whether the amounts and relative rates of synthesis of selected proteins in spinal motoneurons are altered during axonal regeneration. Bulk-isolated amphibian motoneurons will be utilized to investigate changes specifically related to tubulin, actin, acetylcholinesterase (AChE) and choline acetyltransferase (ChAc) in spinal motoneurons after unilateral ventral root section. Enzyme and binding activities, radioactive amino acid incorporation, as well as one- and two-dimensional polyacrylamide gel electrophoresis are employed to determine the magnitude and time course of any change in the activity and/or relative rate of synthesis of each of these four proteins. The possibility of "dedifferentiation" of AChE and ChAc, as well as of changes in the mass and synthesis of other motoneuronal proteins during the axon reaction are also addressed. Together these experiments are expected to provide a variety of useful chemical information about the proteins of normal and regenerating spinal motoneurons and should also aid in the study of spinal motoneurons affected by degenerative disorders.